On Monday, former chairman of the Joint Chiefs of Staff General Hugh Shelton told told Jon Stewart that a Clinton cabinet member proposed letting Saddam kill an American pilot as a pretext for war in Iraq:

This might seem, at first glance, like just an odd, one-off suggestion.

However, as reported by the New York Times and other newspapers, George W. Bush also suggested to Tony Blair that a U.S. plane be painted in United Nations colors so that - if Saddam shot it down - it would create a casus belli. As the Times wrote in 2006:

The memo [confirmed by two senior British officials as being authentic] also shows that the president and the prime minister acknowledged that no unconventional weapons had been found inside Iraq. Faced with the possibility of not finding any before the planned invasion, Mr. Bush talked about several ways to provoke a confrontation, including a proposal to paint a United States surveillance plane in the colors of the United Nations in hopes of drawing fire ....

And it's not just the current war in Iraq. As I've previously pointed out, war is always sold to it's people by artificially demonizing the enemy:

Countries need to lie about their enemies in order to demonize them sufficiently so that the people will support the war.

That is why intelligence "failures" - such as the following - are so common:

And governments from around the world have admitted that - for many years - they have used false flag incidents to sell their people on the wars they wish to launch.

For example:

A major with the Nazi SS admitted at the Nuremberg trials that - under orders from the chief of the Gestapo - he and some other Nazi operatives faked attacks on their own people and resources which they blamed on the Poles, to justify the invasion of Poland. Nazi general Franz Halder also testified at the Nuremberg trials that Nazi leader Hermann Goering admitted to setting fire to the German parliament building, and then falsely blaming the communists for the arson

The CIA admits that it hired Iranians in the 1950's to pose as Communists and stage bombings in Iran in order to turn the country against its democratically-elected prime minister

Israel admits that an Israeli terrorist cell operating in Egypt planted bombs in several buildings, including U.S. diplomatic facilities, then left behind "evidence" implicating the Arabs as the culprits (one of the bombs detonated prematurely, allowing the Egyptians to identify the bombers, and several of the Israelis later confessed) (and see this and this)

As admitted by the U.S. government, recently declassified documents show that in the 1960's, the American Joint Chiefs of Staff signed off on a plan to blow up AMERICAN airplanes (using an elaborate plan involving the switching of airplanes), and also to commit terrorist acts on American soil, and then to blame it on the Cubans in order to justify an invasion of Cuba. See the following ABC news report; the official documents; and watch this interview with the former Washington Investigative Producer for ABC's World News Tonight with Peter Jennings. Official State Department documents show that - only nine months before - the head of the Joint Chiefs of Staff and other high-level officials discussed blowing up a consulate in the Dominican Republic in order to justify an invasion of that country. (While the Joint Chiefs of Staff pushed as a serious proposal for Operation Northwoods to be carried out, cooler heads fortunately prevailed; President Kennedy or his Secretary of Defense Robert McNamara apparently vetoed the plan)

The South African Truth and Reconciliation Council found that, in 1989, the Civil Cooperation Bureau (a covert branch of the South African Defense Force) approached an explosives expert and asked him "to participate in an operation aimed at discrediting the ANC [the African National Congress] by bombing the police vehicle of the investigating officer into the murder incident", thus framing the ANC for the bombing

An Algerian diplomat and several officers in the Algerian army admit that, in the 1990s, the Algerian army frequently massacred Algerian civilians and then blamed Islamic militants for the killings (and see this video; and Agence France-Presse, 9/27/2002, French Court Dismisses Algerian Defamation Suit Against Author)

According to the Washington Post, Indonesian police admit that the Indonesian military killed American teachers in Papua in 2002 and blamed the murders on a Papuan separatist group in order to get that group listed as a terrorist organization.

The well-respected former Indonesian president also admits that the government probably had a role in the Bali bombings

As reported by BBC, the New York Times, and Associated Press, Macedonian officials admit that the government murdered 7 innocent immigrants in cold blood and pretended that they were Al Qaeda soldiers attempting to assassinate Macedonian police, in order to join the "war on terror".

Former Department of Justice lawyer John Yoo suggested in 2005 that the US should go on the offensive against al-Qaeda, having “our intelligence agencies create a false terrorist organization. It could have its own websites, recruitment centers, training camps, and fundraising operations. It could launch fake terrorist operations and claim credit for real terrorist strikes, helping to sow confusion within al-Qaeda’s ranks, causing operatives to doubt others’ identities and to question the validity of communications.”

U.S. intelligence officers are reporting that some of the insurgents in Iraq are using recent-model Beretta 92 pistols, but the pistols seem to have had their serial numbers erased. The numbers do not appear to have been physically removed; the pistols seem to have come off a production line without any serial numbers. Analysts suggest the lack of serial numbers indicates that the weapons were intended for intelligence operations or terrorist cells with substantial government backing. Analysts speculate that these guns are probably from either Mossad or the CIA. Analysts speculate that agent provocateurs may be using the untraceable weapons even as U.S. authorities use insurgent attacks against civilians as evidence of the illegitimacy of the resistance.

At the G20 protests in London in 2009, a British member of parliament saw plain clothes police officers attempting to incite the crowd to violence

There are many other instances of false flag attacks used throughout history proven by the historical evidence. See this, this and this. The above are only some examples of governments admitting to using false flag terror.